Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

Influences of solid particles on the formation of the third phase crud during solvent extraction

The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud.

Influence of Particles on the Loading Capacity and the Temperature Rise of Water Film in Ultra-high Speed Hybrid Bearing

Ultra-high speed machining technology enables high efficiency, high precision and high integrity of machined surface. Previous researches of hybrid bearing rarely consider influences of solid particles in lubricant and ultra-high speed of hybrid bearing, which cannot be ignored under the high speed and micro-space conditions of ultra-high speed water-lubricated hybrid bearing. Considering the impact of solid particles in lubricant, turbulence and temperature viscosity effects of lubricant, the influences of particles on pressure distribution, loading capacity and the temperature rise of the lubricant film with four-step-cavity ultra-high speed water-lubricated hybrid bearing are presented in the paper. The results show that loading capacity of the hybrid bearing can be affected by changing the viscosity of the lubricant, and large particles can improve the bearing loading capacity higher. The impact of water film temperature rise produced by solid particles in lubricant is related with particle diameter and minimum film thickness. Compared with the soft particles, hard particles cause the more increasing of water film temperature rise and loading capacity. When the speed of hybrid bearing increases, the impact of solid particles on hybrid bearing becomes increasingly apparent, especially for ultra-high speed water-lubricated hybrid bearing. This research presents influences of solid particles on the loading capacity and the temperature rise of water film in ultra-high speed hybrid bearings, the research conclusions provide a new method to evaluate the influence of solid particles in lubricant of ultra-high speed water-lubricated hybrid bearing, which is important to performance calculation of ultra-high speed hybrid bearings, design of filtration system, and safe operation of ultra-high speed hybrid bearings.

ON EQUATION OF DISCRETE SOLID PARTICLES' MOTION IN ARBITRARY FLOW FIELD AND ITS PROPERTIES

The forces on rigid particles moving in relation to fluid having been studied and the equation of modifications of their expressions under different flow conditions discussed, a general form of equation for discrete particles' motion in arbitrary flow field is obtained. The mathematical features of the linear form of the equation are clarified and analytical solution of the linearized equation is gotten by means of Laplace transform. According to above theoretical results, the effects of particles' properties on its motion in several typical flow field are studied, with some meaningful conclusions being reached.

A Test Study of 50% Lightning Impulse Breakdown Voltage on Rod-Plane Gap with Two-Phase Mixture of Gas and Solid Particles

A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission （IEC） standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.

Effect of solid particles on gear tooth failure

The failure of spur gears operating in highly contaminated media was studied. In fact, the effect of the presence of solid particles in gear mechanisms during surface tooth contact was observed. It is shown that the solid contaminants lead to significant wear in the first few operating cycles, in zones with a high rate of sliding. The scanning electron microscopy(SEM) images show clearly that the wear is more significant for a dry contact in the presence of larger size particles. Indeed, the presence of contaminants leads to an increase in friction, and therefore raises the temperature and the vibration levels when the operation of gear mechanism becomes very severe especially for a dry contact under the effect of larger size particles. On the other hand, we have tried to obtain a better understanding and a good description of wear debris distributions in gear mechanisms by using unimodal, single distribution models(Weibull and three-parameter Weibull).

RESEARCH ON STABILITY OF MOVING JET CONTAINING DENSE SUSPENDED SOLID PARTICLES

The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.

Mssbauer Effect in Ultrafine Particles with Fe-C Solid Solution,γ-Fe and Fe_3C Phases

Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.

Investigation of Movement and Deposition Behaviors of Solid Particles in Hydraulic Water Reservoir via the CFD‑DEM Coupling Method

Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction,system failures,and component damage.The hydraulic reservoir will deposit the contamination and store hydraulic fluid.To investigate its purification ability for solid contamination,experiments and simulations for the motion and deposition status of the typical hydraulic system particles are carried out to reveal the interaction of particles and fluid in hydraulic water reservoirs.The results show that the CFD-DEM coupling method could predict the accurate deposition position of iron particles and sand particles when ignoring the small-scale turbulence effect in the flow field.Besides,the particle motion traces and deposition patterns in the reservoir illustrate that the flow development on the bottom surface results in the particles turning,and particles tend to settle in the low flow energy position.The motion of particles is also linked to particles Stokes number,and the same-size sand particles are easily driven by the fluid.The contribution of this paper could provide a guide for predicting the particle motion and deposition pattern in the hydraulic reservoir.

Numerical evaluation of virtual mass force coefficient of single solid particles in acceleration

Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system.In this work the accelerating motion of a single solid particle is mathematically formulated and solved using the vorticity-stream function formulation in an orthogonal curvilinear coordinate system.The total drag coefficient was evaluated from the numerical simulation in a range of the Reynolds number(Re)from 10 to 200 and the dimensionless acceleration(A)between2.0 to 2.0.The simulation demonstrates that the total drag is heavily correlated with A,and large deceleration even drops the drag force to a negative value.It is found that the value of virtual mass force coefficient(CV)of a spherical particle is a variable in a wide range and difficult to be correlated with A and Re.However,the total drag coefficient(CDV)is successfully correlated as a function of Re and A,and it increases as A is increased.The proposed correlation of total drag coefficient may be used for simulation of solid–liquid flow with better accuracy.

RESEARCH ON STABILITY OF INTERFACE OF JET CONTAINING SUSPENDED SOLID PARTICLES

The stability equation of interface of two-phase jet and the corresponding particle-gas disturbance velocity ratio equation are derived by means of the phase-coupled model. The stability nares of interface of two-phase jet for different particle properties and the corresponding particle-gas disturbance velocity ratio curves are given out through numerical computation. Further, several important conclusions on effect of particle property on growth and propagation of disturbance of interface of two-phase jet and particle disturbance property me presented on the basis of analyses of the obtained stability curves and particle-gas disturbance velocity ratio curves. These important conclusions can play a guiding role in studying development of two-phase jet and executing artificial controls over it in project practice.

EFFECT OF SUSPENDED SOLID PARTICLES ON UNSTABILITY OF TWO-DIMENSION MIXING LAYER

By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then, by solving the corresponding eigen-value equations with numerical computational method, the relation curves between perturbation frequency and spacial growth rate of the mixing layer for the varying particle loading, ratio of particle velocity to fluid velocity and Stokes number are got. Sever al important conclusions on the effect of suspended solid particles on unstability of the mixing layer are presented in the end by analyzing all the relation curves.

Experimental study on solid particle migration and production behaviors during marine natural gas hydrate dissociation by depressurization

Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.

Effect of structural characteristics on the transport characteristics of solid particles in the thermal storage and release system of circulating fluidized bed

Coal-fired power generation stands as the most economically viable modulating power source in present-day China.It holds the potential to offer prospective solutions to the challenges posed by the rapid expansion of intermittent,unpredictable,and unstable renewable energy sources.Solid particle thermal storage technology emerges as an effective means to enhance the flexibility of coal-fired circulating fluidized bed power units.To attain an optimized structure for the solid particle thermal storage and release system in circulating fluidized bed units,experimental research was conducted on a 0.1 MWth circulating fluidized bed test platform.This study delved into the impact of ash storage bin geometries and the shapes of their feed-discharge valves on the control properties of solid particle transportation.The experimental outcomes reveal that employing inverted m-shaped valve and dual U-shaped valves for feed control,alongside U-shaped valves and N-shaped valves for discharge control,both enable efficient and rapid storage and release of solid particles within the circulating fluidized bed.Under similar air distribution conditions,the inverted m-shaped valve exhibits lower conveying energy consumption than the dual U-shaped valves,while the N-shaped valve excels in control characteristics over the U-shaped valve.Furthermore,the inverted m-shaped valve and the N-shaped valve demonstrate optimal overflow port heights,and the ash storage bin exhibits an optimum height-to-diameter ratio.

Effect of Air Distribution on the Transport Characteristics of Solid Particles in the Thermal Storage and Release System of Circulating Fluidized Bed

Solid particle heat storage technology offers a potential solution to the challenges posed by the significant growth of renewable energy sources,particularly in terms of grid security and stability.Consequently,it has the capability to optimize the energy utilization efficiency of the power system.In order to investigate the transport regulation characteristics of solid particles in the thermal storage and release system of a circulating fluidized bed(CFB),a test rig with a capacity of 0.1 MW(th)was established.This rig was utilized to systematically study the transport regulation characteristics of solid particles under the double U-type valve feed structure and U-type valve discharge structure.The experimental findings indicate that the system's design enables efficient and rapid storage and release of solid particles in the CFB.The air distribution mode,specifically the double U-type valve feed structure and the U-type valve discharge structure,significantly influence the feed and discharge characteristics of the ash storage bin.It was observed that the impact of loose air on these characteristics is more substantial than that of the return air,irrespective of the feed structure or the return structure.When adjusting the feed and discharge rate,it is recommended to adopt a scheme that involves coarse adjustment through loose air and fine adjustment through return air.

Process Intensification in Pneumatically Agitated Slurry Reactors

Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.

Impact of inter-particle collision on elbow erosion based on DSMC-CFD method

In this work,computational fuid dynamics(CFD)is used to study elbow erosion due to a gas-solid two-phase fow.In particular,the direct simulation Monte Carlo(DSMC)method is used to study the impact of inter-particle collision on the erosion behavior.The two-way coupled Euler-Lagrange method is used to solve the gas-solid fow,and the DSMC method is used to consider the collision behavior between particles.The efects of key factors,such as the particle concentration distribution and inter-particle collision,on the erosion ratio are evaluated and discussed.The efectiveness of the method is verifed from experimental data.The results show that the inter-particle collision signifcantly infuences the particle movement path and erosion ratio.When the inter-particle collision is considered,the maximum erosion position is ofset.The erosion model proposed by Oka et al.,who used the DSMC method,agrees best with the experimental data,and the average percentage error decreases from 39.2 to 27.4%.

Progress in Bio‑inspired Anti‑solid Particle Erosion Materials:Learning from Nature but Going beyond Nature

Solid particle erosion is a common phenomenon in engineering fields,such as manufacturing,energy,military and aviation.However,with the rising industrial requirements,the development of anti-solid particle erosion materials remains a great challenge.After billions of years of evolution,several natural materials exhibit unique and exceptional solid particle erosion resistance.These materials achieved the same excellent solid particle erosion resistance performance through diversified strategies.This resistance arises from their micro/nanoscale surface structure and interface material properties,which provide inspiration for novel multiple solutions to solid particle erosion.Here,this review first summarizes the recent significant process in the research of natural anti-solid particle erosion materials and their general design principles.According to these principles,several erosion-resistant structures are available.Combined with advanced micro/nanomanufacturing technologies,several artificial anti-solid particle erosion materials have been obtained.Then,the potential applications of anti-solid particle erosion materials are prospected.Finally,the remaining challenges and promising breakthroughs regarding anti-solid particle erosion materials are briefly discussed.

EXPERIMENTAL INVESTIGATION ON PARTICLE EFFECT IN PISTON RING-CYLINDER LUBRICATION

To study the tribological properties of the piston ring-cylinder liner in liquid-solid lubrication, the experiment is carried out on a modified piston ring-cylinder liner tester. Two kinds of liquid-solid lubricants are used, one with ultra-dispersed diamond （UDD） nano-particles suspending in pure lubricant, the other with micro-sized MoS2 particles. The particle concentrations are 0%, 0.02% and 0.1% by weight. The experimental temperature is 30℃ and 75℃ respectively. The results show that with the presence of ultra-dispersed diamond particles, the load when scuffing failure occurs is increased. For the lubricant contains MoS2 particles, the scuffing load is decreased. The liquid-solid lubricant also affects the thermal behavior of piston ring-cylinder liner. The surface bulk temperatures of cylinder liner specimen are measured. It has been seen that liquid-solid lubricant used in this research tends to improve the thermal properties generally and the measured friction forces also decreases with the presence of UDD nano-particles. The surface bulk temperature when scuffing occurs is also measured. The results show that the size effect and environment temperature have obvious influence on scuffing load and scuffing temperature. With some new findings, this work is an important complement to the existing research on particle effect on lubrication, because the existing results only show one aspect of this problem.

Experimental Study on the Erosion of Pipelines under Different Load Conditions

The influence of the material stress state induced by internal and external forces on the erosion rate of pipelines has rarely been investigated in the literature.In order to fill this gap,using a tensile tester machine,a two–phase gas–solid particles jet erosion test was carried out considering a 316L stainless steel under different tensile stresses and different erosion angles.The results show that:1)In the elastic range,with the increase of stress,the erosion rate manifests a rising trend;2)In the metal plastic range,the increase of stress leads to a decrease of the erosion rate;3)The erosion rate at a small erosion angle is more sensitive to the increment of stress.The present research demonstrates that the combined effect of erosion and material internal stress can contribute to determine the effective resistance of the vulnerable parts of piping systems(such as elbows or similar components).